Effects of fentanyl on cellular immune functions in man

In order to analyze the effects of the opioid agonist fentanyl on cells of the innate immune system, seven healthy individuals were treated intravenou sly with the opioid fentanyl and five subjects received a placebo. Respirat ory burst of polymorphonuclear cells (PMNC) and phenotypes of peripheral bl ood lymphocytes (PBL) were analyzed from blood samples drawn before, 15 and 30 min after fentanyl or placebo application. In addition, in vitro effect s of fentanyl on natural killer (NK) activity was assessed. Fentanyl admini stration affected neither superoxide production of PMNC nor circulating num bers of Band T-lymphocytes. In contrast, NK cell (CD16(+)/CD56(+)) numbers significantly increased in response to fentanyl. However, no direct influen ce of fentanyl on NK cell function in vitro could be detected. These result s suggest a transient effect of fentanyl on NK cell circulation which seeme d to be centrally mediated rather than a direct effect of this opioid on NK cells. (C) 1999 International Society for Immunopharmacology, Published by Elsevier Science Ltd. All rights reserved.